High surface area polymer actuator with gas mitigating components

ABSTRACT

A polymer actuator component and a polymer actuator assembly, power supply and method of using the activation are described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/018,024, filed Jan. 31, 2011, which claims priority from U.S.Provisional Application Ser. No. 61/300,345, filed Feb. 1, 2010, andfrom U.S. Provisional Application Ser. No. 61/332,760, filed May 8,2010, and from U.S. Provisional Application Ser. No. 61/432,108, filedJan. 12, 2011, the contents of which are incorporated hereby byreference

STATEMENT OF GOVERNMENT INTEREST

This invention was made in part with Government support under contractnumber 0848528 awarded by the National Science Foundation. TheGovernment may have certain rights in the invention.

FIELD

The present invention relates to volume changing materials. Moreparticularly, the invention concerns polymeric materials that changevolume in response to a pH change. The materials advantageously areemployed in activators that may be used, for example, as actuators forpumps for administration of therapeutic liquids and will be described inconnection with such utility, although other utilities are contemplated.

BACKGROUND

Actuators are devices that generate displacement or force for variousapplications. These can take on many forms such as motors, aircylinders, hydraulic cylinders, and electromagnetic solenoids to name afew. These actuators are utilized for many different applications andhave been in use for decades.

A particular class of polymeric based actuators that have been developedare polymer actuators based on elastic epoxy hydrogel polymers. Suchactivators work by creating ionic imbalances near electrodes usingpositive or negative electrical charges at an electrode in contact withor in close proximity to the polymer and an ionic species of theelectrolyte. By increasing the density or the number of the aminegroups, such as secondary and primary amines, an increase in swellingpressure is attained in the hydrogel. This also has an effect on theswelling and deswelling times.

One way of achieving this is by incorporating Polyamidoamine (PAMAM)polyether dendrimers, poly(propylene imine (PPI)-dendrimers, aminofunctionalized dendrimers, or combinations thereof, as part of thepolymer structure. Dendrimers are highly branched and offer superiornumbers of polymer linkage points. They also are commercially availablewith primary amino surface groups and core amino groups. This makesengineering of the hydrogel possible so that specific performanceparameters such as the pressure the gel can produce is determined byformula ratios of materials or by controlling the organization, size andnumber of branches in polymer structure itself. Hydrogel density andporosity is controlled by the amount of amine functionality andmolecular weight of the polyether amines. Hydrogel density and porosityis also controlled by amount of polyethylene glycol diglycidyl etherand/or by the ratio of H₂O or solvent used to polymerize the materials.

A preferred ether for this gel is polyethyleneglycol-dodecylether(polyEGDE), but other ethers also can be used such ascyclohexanedimethanol diglycidyl ether. These ethers produce a veryclear and strong hydrogel that reacts hydrophobically to high pH aqueoussolutions and swells when exposed to low pH or acidic solutions.Hydrogel density and porosity also can be controlled by adding an amountof oxidizer to the polymer during polymerization. Whether in solution ordry these oxidizers can be further activated chemically electrically orby photons during polymerization to achieve desired properties.

Ionic hydrogel swelling kinetics are achieved by a difference in pH,ions, cations or protons between a solution outside of the hydrogel anda solution inside of the hydrogel or the polymer composition of thehydrogel. These performance characteristics can be controlled severalways. For example, adding acid to the polymer during polymerizationcreates a hydrogel that has a higher pH swelling property. Hydrogelswelling kinetics also can be controlled by adding salts or alkalisolutions to the polymer during polymerization. This is accomplished bychemical, electrical, electrochemical, photo or photochemical excitationof the epoxy polymer or solution that it is hydrated with.

It is possible to create an electro activated polymer (EAP) by hydratingthe epoxy hydrogel in an electrolyte, inserting an electrode into thegel, and spacing a second electrode a short distance from the hydrogeland running low amounts of current through the electrodes. For example,epoxy hydrogel swelling may be increased in the region of a platinumelectrode using saline as an electrolyte fluid. When the polarity isreversed, the hydrogel will deswell or contract. Control of hydrophobicand hydrophilic properties also can be achieved by these methods.

A challenge with these polymer actuators is to generate forces andstrain rates of actuation that are sufficient for pumping fluids.

Another challenge with such polymeric actuators is the generation of gasduring operation. Polymeric actuators utilizing electrodes and aqueouselectrolytes are particularly advantageous for high efficiency actuationbut may hydrolyze out oxygen and hydrogen.

Gases produced in a polymer actuator are undesirable for the effectsthey may have on charge transfer and the mechanical system. By producingan insulating pocket, a gas bubble will impede charge transfer throughthe system. This effectively lowers the surface area of the electrodeand/or the polymer which reduces the rate of expansion of the polymer.To make matters worse, the gas pocket is variable and unpredictable insize and precise composition, reducing accuracy of any device utilizinga polymeric actuator.

Also, gas expansion may produce an apparent expansion of an actuatorthat later relaxes due to compression or absorption of the gas. Gasproduction thus reduces repeatability, predictability, and accuracy ofthe actuator.

Compounding these consistency problems is the inconsistent adhesion ofactuator polymer to a non-reactive substrate. Hydrogels are prone todelamination and typically are not stable in aqueous environments,hindering, for example, thin film characterization and use in aqueousmedia. Adhesion may require solutions that increase the number ofchemicals and process steps leading to increased complexity, and may usechemicals that are not environmentally benign.

There is therefore a need for an actuator that can produce high rates ofactuation without the shortcomings of hydrolysis or other gasgeneration.

There is further a need for a hydrogel actuator that is convenientlyadhered to a hydrophobic surface.

Conventional actuators do not meet the full need for such anapplication. Furthermore state of the art polymer actuators do notisolate and create distinct ionic or pH boundaries of the electrolyte atthe anode or cathode side of the electrodes.

Typical electrode materials for polymer actuators are metals, carbonsand some conductive polymers. The type of electrode is somewhatdependent on the type of actuator and electrolytic chemistry needed tocreate the desired response. One drawback to using most metals is thatthey typically are not stable for both the oxidation and redox reactionat each electrode. Nobel metals such as gold and platinum can be useddue to their stability but are very expensive and not practical forindustrial type use. Other materials such as carbon and graphite willwork but have difficult working mechanical properties making them notpractical, and conductive polymers are very limited in their chemicalcompatibility to other polymers. Another drawback all electrodes have iselectrochemical gas generation at the electrode surface interface withthe electrolyte. The generation of gas, both in type and volume, isdependent on the polarity of the electrode and the amount of electricalcurrent applied to the electrodes in an actuator or actuator assemblyand the electrolyte. Gas creates a significant problem of compressiblepressure in closed or sealed actuator systems, and can actually outpacethe polymer actuation or volume change thereby creating unreliableresults in actuation cycles.

SUMMARY

The present invention overcomes the aforesaid and other problems of theprior art. The invention, in one aspect, provides a polymer actuatorassembly having an anode and a cathode separated by a porous membrane inan electrolyte, a metal hydride material in contact with the surface ofone or more of the electrodes, and a polymeric actuator in contact withthe anode or the cathode. The porous membrane acts as a barrier orseparator material and eliminates or reduces comingling of the ionic orpH regions, substantially increasing the response, accuracy, time andvolume changes of the actuator material, as well as improving the rangeof electrode materials and configurations of the cathode and anodeelectrodes within the device.

The electrodes in solution with the porous membrane facilitatemodulation of the pH around the polymeric actuator via charges or ionicseparation. The electrolyte may be aqueous or nonaqueous. The polymericactuator may be configured to expand or contract in response to pH orchemical changes in the electrolyte induced by an electrical potentialdifferential in the electrodes.

The actuator assembly may further provide a sealed flexible outerhousing enclosure allowing sealed entrance or exit points for theelectrodes. In an alternative embodiment, the assembly provides a secondpolymeric actuator such that each polymeric actuator is adjacent to oneof the electrodes and both actuators are configured to expand orcontract simultaneously when an electric potential differential isapplied to the electrodes.

The polymeric actuator and the electrode in contact with the polymericactuator may be sealed inside a flexible container or bag made of thesame material as the porous membrane with a portion of the electrodeexiting the flexible container. The portion of the electrode outside ofthe flexible container is then insulated from the electrolyte by porousmembrane material to facilitate actuation when the electric potentialdifferential is applied to the electrodes. The flexible container orhag, or at least a portion of the flexible container or bag preferablyis composed of an elastomeric material. A rigid structure that ispervious to the electrolyte or solution by being, for example, porous,may surround the polymer actuator material, at least in part, tofacilitate the direction of actuation.

The surface area of the polymeric actuator exposed to the actuatingstimulus may be increased by pulverizing or grinding the polymericactuator material into smaller particles or particulates. Theparticulates of the actuating material may then form a slurry with theelectrolyte. The particulates may be enclosed in a flexible, porousenclosure with the electrode in contact with the exterior surface of theenclosure, or with the electrode penetrating the enclosure to be indirect contact with the particulates and the electrolyte immediatelysurrounding the particulates. The flexible enclosure may be contained,at least in part, in a rigid porous container that directs the action ofactuation while allowing fluidic flow of electrolyte through the rigidcontainer.

The actuator assembly may further comprise a gas absorbant material suchas activated carbon. Alternatively, gas created in the electrolyte orsolution may be collected in a storage area outside of the sealedflexible housing. The storage area is in fluid connection with theelectrolyte to allow selective flow of gas, without removing electrolyteinto the storage area.

The polymeric actuator of the actuator assembly may act as a platen orpiston. Moreover, the electrodes of the actuator assembly may beconfigured to allow in-line electrical connectivity of a series ofactuators in a more complex system. The assembly may include aprogrammable controller and a power source to create the electricalpotential differential in the electrodes power the programmablecontroller. One or more sensors may communicate feedback to thecontroller for more automatic operation of the actuator assembly. Theactuator assembly or a plurality of actuator assemblies in a desiredconfiguration may be used to pump a fluid.

The invention in another aspect provides a polymeric actuator assemblyincluding a housing, a first electrode and a second electrode, and aelectrolyte. The electrodes are separated by a membrane to maintain a pHdifference between the electrolyte surrounding the respective electrodeswhen a voltage is applied between the first and second electrodes. Theassembly may include a plurality of polymeric actuators disposed near anelectrode that respond to a pH change within the electrolyte.

The polymeric actuator may have increased surface area by pulverizing orgrinding the actuating material into granules. The porous container is apolymeric bag, and the granules of actuating material form a slurry withthe electrolyte within the bag.

In yet another aspect of the invention, a polymeric actuator componentcomprises an actuating polymer that increases volume in response to astimulus cross-linked to a hydrophobic polymer. The actuating polymerand the hydrophobic polymer comprise an ether epoxide and an NHreactant, and preferably the NH component is common to both polymers.The epoxide in the actuating polymer is a hydrophilic di-epoxide, suchas polyethylene diglycidyl glycol ether. The epoxide in the hydrophobicpolymer is a hydrophobic di-epoxide, such as neopentyl diglycidyl etheror polypropylene diglycidyl glycol ether. The NH reactant may be apolyether amine, such as JEFF AMINE® T-403 available from HuntsmanCorporation. The hydrophobic polymer may further comprisepolyethyleneimine and water to decrease polymerization time.

The ratio of epoxide to NH reactant in the actuator polymer withoutdendrimers typically is between about 1 to 2 and about 1 to 10,preferably about 1 to 2.85, and the ratio of epoxide to NH reactant inthe hydrophobic polymer typically is between about 1 to 1.5 and about 1to 3, preferably about 1 to 2.0. By incorporating dendrimers the ratioof epoxide to NH reactant can become significantly different dependenton the number of NH sites on each dendrite molecule these can range from4 NH units in a 1^(st) generation molecule to over 5,000 in a tenthgeneration molecule. Polymers incorporating dendrimers would have a muchlarger epoxide to NH unit ratio and could easily be between 1 to 4 and 1to thousands of NH units.

The composite hydrogel material of the invention may be used to producean actuator polymer that is sealed in a defined volume by thehydrophobic polymer, or an actuator polymer that is protected from theexternal environment by the hydrophobic polymer. The composite hydrogelmaterial may be used as a sensor material structure, gel electrolytematerial, selective ion permeable membrane, liquid filtration andtreatment component, wound care membrane or acid scavenging material, aswell as many other applications that would be recognized by those havingskill in the art.

The invention in another aspect provides a polymeric actuator materialmade by polymerizing an ether reactant including both a hydrophilicether and a hydrophobic ether and an epoxide. The actuation speed orflexibility of the material may be adjusted according to the ratio ofthe dominant ether reactant to the lesser ether reactant. In thisaspect, the ratio of epoxide to NH reactant typically is preferablybetween about 1 to 2.5 and about 1 to 3, more preferably about 1 to2.85. The ratio of hydrophilic ether to hydrophobic ether is betweenabout 100 to 1 and about 1 to 100, typically about 99 to 1.

In yet another aspect, the present invention provides improvements inthe electrodes of polymer actuators. An electrode capable of doublelayer capacity or charge storage within but not limited to an activatedcarbon layer applied or bonded to the electrode is desirable to controlgas generation at the electrode and electrolyte interface in a polymeractuator. This aspect of the invention provides a device for activatinga polymer actuator, including one or more polymer actuators, eachactuator having one or more double layer capacitor electrodes. Thepolymer actuators are either activated electrically or activatedchemically. The double layer capacitor electrodes are in an electrolytethat may be either aqueous or non-aqueous. The electrodes may beconnected to a discharge circuit and a controller, wherein thecontroller is configured to open and close the discharge circuit at apredetermined time or upon the accumulation of a specified amount ofcharge in the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views, wherein:

FIGS. 1A and 1B depict exemplary composite epoxy polymer actuatorcomponents before and after activation according to one aspect of thepresent invention;

FIG. 1C depicts an exemplary array of composite epoxy polymer actuatorcomponents in accordance with the present invention;

FIG. 2A depicts an exemplary actuator assembly of the present inventionin schematic form;

FIG. 2B depicts another exemplary actuator assembly of the presentinvention in schematic form including, among other things, a pluralityof actuating areas;

FIG. 2C depicts another exemplary actuator assembly of the presentinvention in schematic form including, among other things, a hydridematerial surrounding each electrode of the actuator assembly;

FIG. 3A depicts an exemplary actuator assembly of the present inventionin schematic form including, among other things, a gas absorbentmaterial;

FIG. 3B depicts an exemplary actuator assembly of the present inventionin schematic form including, among other things a separate chamber tosequester gas(es) that may be produced in the actuator; and

FIG. 4 depicts an actuator assembly in schematic form, including adouble layer capacitor electrode, according to one aspect of the presentinvention.

DETAILED DESCRIPTION

In the following description directional or geometric terms such as“upper”, “lower”, and “side” are used solely with reference to theorientation of the Figures depicted in the drawings. These are not toimply or be limited to a direction with respect to a gravitationalreference frame but are utilized to distinguish directions relative toeach other. Because components of the invention can be positioned in anumber of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention.

Details in the various embodiments such as how current or wiring isrouted to electrodes from power supplies are left out for illustrativesimplicity since various methods of such routing is known in the art.The term “electrolyte” refers to and includes all aqueous, non-aqueous,polymer and solid electrolytes, including those that are generally wellknown in the art. The term “electrodes” refer to anodes and cathodescommonly used in electrochemical systems that are made of materials wellknown in the art such as metals, carbons, graphenes, oxides orconducting polymers or combinations of these. The term “separator”refers to any nano, micro or macro porous material that allows targetedions to move through or across it faster than surrounding ion containingmedia. The term “ion” refers to ions and ion species as well as anion,cation, electrons and protons, and concentration values of these. Theterm “housing” refers to the exterior portion of the device which may befabricated from flexible material, rigid material, elastic materials,non elastic materials or a combination of these such as rubbers,silicone, polyurethane, metalized polymer films and other plastics orpolymers known in the art. The housing is configured to allow movementand expansion of the internal parts as well as allowing for filling thedevice with electrolyte, acting as a container and barrier to stop anyelectrolyte leakage or evaporation, allowing electrodes to makeelectrical contact with power source as well as to enter and exit thehousing, if needed, and also the ability to vent any unwanted gasgeneration, if needed.

Referring to the drawings, an actuator 100 is comprised in part of apolymeric actuating material. In an exemplary embodiment these polymeractuators are formed from ion or pH responsive epoxy polymer Hydrogelbased polymers. Examples of such polymers are described in commonlyowned WIPO patent application WO 2008/079440 A2, Entitled ‘SUPER ELASTICEPOXY HYDROGEL”, filed on Jul. 10, 2007 and published on Jul. 3, 2008.Other polymer actuator examples may contain polymers which have ionicfunctional groups, such as carboxylic acid, phosphoric acid, sulfonicacid, primary amine, secondary amine, tertiary amine, and ammonium,acrylic acid, methacrylic acid, vinylacetic acid, maleic acid, metakurir yl oxy ethylphosphoric acid, vinylsulfonic acid, styrene sulfonicacid, vinylpyridine, vinylaniline, vinylimidazole, aminoethyl acrylate,methylamino ethyl acrylate, dimethylamino ethyl acrylate, ethylaminoethyl acrylate, ethyl methylamino ethyl acrylate, diethylamino ethylacrylate, aminoethyl methacrylate, methylamino ethyl methacrylate,dimethylaminoethyl methacrylate, ethylamino ethyl methacrylate, ethylmethylamino ethyl methacrylate, diethylamino ethyl methacrylate,aminopropyl acrylate, methylaminopropyl acrylate, dimethylaminopropylacrylate, ethylaminopropyl acrylate, ethyl methylaminopropylacrylate, diethylamino propylacrylate, aminopropyl methacrylate, methylaminopropyl methacrylate, dimethylaminopropyl methacrylate,ethylaminopropyl methacrylate, ethyl methylaminopropyl methacrylate,polymers, such as diethylamino propyl methacrylate, dimethylaminoethylacrylamide, dimethylaminopropylacrylamide, and alpha kurir yl oxy ethyltrimethylammonium salts, are reported to be of use but these examplesare for reference and not intended to limit the scope or use of theinvention.

The invention in one aspect comprises new actuating polymers comprisedof hydrophobic materials cross linked with smart hydrogel polymers usingmultiple di-epoxides or polyepoxides as the cross linking mechanism toadhere the materials together at the molecular level. The compositematerial also may be formed by using a single diepoxide or polyepoxideand then cross linking different layers of material via the polyaminecomponents such as JEFF AMINE® with different functionalities or polymerchains and back bones.

Previously filed PCT/US2007/073188 (hereby incorporated in itsentirety), describes unique epoxy hydrogel polymers formed by reacting apolyether amine with a polyglycidyl ether. The resulting polymer is asuper elastic hydrogel having various applications. The epoxy hydrogelcan be produced by mixing ratios of “ether reactants” such aspolyethylene glycol diglycidyl ether and polyoxyalkyleneamines and H2Oresulting in an aqueous polymerization of the materials. Particularlypreferred are polyoxyalkyleneamines such as commercially available fromHuntsman Corporation under the brand name JEFF AMINE® and otherpolyether amines as an “epoxy” component that is reacted with variousethers to form epoxy hydrogels. The polyoxyalkyleneamines containprimary amino groups attached to the terminus of a polyether backbone.They are thus “polyether amines.” The polyether backbone is based eitheron propylene oxide (PO), ethylene oxide (EO), mixed propyleneoxide/ethylene oxide or may contain other backbone segments and variedreactivity provided by hindering the primary amine or through secondaryamine functionality. In one embodiment of the invention, hydrophilicvariants of hydrogel polymer actuators are cross linked based on JEFFAMINE® T-403 and Polyethylene digycidyl glycol ether to hydrophobicvariants of the gel by changing the diglycidyl (ether reactant)component and keeping the same epoxy-JEFF AMINE® T-403 component.

Referring in particular to FIG. 1A, simple cylinders 10 comprised ofhalf hydrophilic actuator material 12 and half non actuating hydrophobicmaterial 14 cross linked together at the molecular level may be cast.The actuator material 12 is first placed into a mold or cast andpartially cured. Then, a second material is added to the mold and bothmaterials are allowed to totally cure. Ratios of di-epoxides to NH maybe varied, and both neopentyl diglycidyl ether and polypropylenediglycidyl glycol ether may be substituted for the polyethylenediglycidyl glycol ether used in the actuator material. A mixture of JEFFAMINE® T-403 and Neopentyl glycol diglycidyl ether yields a polymer withhydrophobic properties advantageous to actuator applications. In thisway, two or more types of epoxy polymers may be adhered together eventhough they have very different properties.

In a specific embodiment, the hydrophobic polymer 14 is bonded to theactuator material 12. In FIG. 1C the hydrophobic polymer 14 is bonded tothe actuator hydrophilic material 12 with addressable electrodes 6 and 7electrically connected to the controller sensor or sensors and powersource. A number of different chemicals may be added to JEFF AMINE®T-403 in order to form a polymer with both hydrophobic properties andthe ability to bind to an actuator gel such as that described inpreviously filed PCT/US2007/073188. For example, neopentyl glycoldiglycidyl ether may be added to JEFF AMINE® T-403 with an Epoxide/NHReactant ratio of 1 to 2.85, the same Epoxide/NH Reactant ratio presentin the standard actuator gel formulation. To ensure promptpolymerization, the ratio of epoxide/NH Reactant ratio may be decreased.Neopentyl glycol diglycidyl ether and JEFF AMINE® T-403 mixtures with anEpoxide/NH Reactant ratio of 1 to 1.7, 1.8, 1.9, and 2.0 were all foundto successfully polymerize after heating at 60 degrees C. for 5 hoursand further curing at room temperature for 72 hours. The hydrophobicityof the polymers with these ratios yielded an approximate maximum ofabout 8-10% swelling after storage in water for up to three weeks.Furthermore, as the Epoxide/NH Reactant ratio is increased, theelasticity of the resultant polymer is also increased. As a result, amixture of JEFF AMINE® T-403 and neopentyl glycol diglycidyl ether withan Epoxide/NH Reactant ratio of 1 to 2.0 displays excellent adhesionwith the actuator polymer 12, not only after curing, but also withhydration.

If desired, the hydrophobicity may be increased and the time requiredfor polymerization decreased. Poly (propylene glycol) diglycidyl ether(PPGDGE) may be added to a mixture of Neopentyl glycol diglycidyl etherand JEFF AMINE® T-403, maintaining an Epoxide/NH Reactant ratio of 1 to2.0 or more Polymers with 10%, 26%, and 50% PPGDGE were synthesized andstored in water to test their hydrophobicity or resistance to swelling.All gels swelled between 12% and 15% after storage in water for twoweeks. Further, it was surprisingly found that the addition of PPGDGEresults in a decrease in polymer elasticity as compared to the baseNeopentyl glycol diglycidyl ether and JEFF AMINE® T-403 polymer.

In order to decrease gel curing time, Polyethyleneimine (1300 molecularweight) may be added to the base Neopentyl glycol diglycidyl ether andJEFF AMINE® T-403 gel. The addition of 10% and 15% polyethyleneiminealong with 10% water results in gels that polymerize more quickly. Thegels completely polymerized after heating at 60 degrees C. for 5 hoursand did not require further curing at room temperature to decrease gelstickiness.

The advantage of faster polymerization may be accompanied by a decreasein hydrophobicity. These gels including Polyethyleneimine were found toswell between 23% and 32% after storage in water for two weeks.Therefore, polymers with an increased hydrophobicity and decreasedpolymerization time are possible, but may be accompanied by performancetradeoffs, particularly in the hydrophobicity of the resultant polymer.

The length of the polymer chain and amine ratio versus Epoxide/NHReactant ratios also may decrease polymerization time in a hydrophilicactuator gel. For example, varying compositions were evaluated usingPolyethyleneimine, (branched polymers similar to Epomin SP-012) low mol.Wt. 50 wt. % soln. in water, both 2000 and 1300 molecular weights.Resulting gels were able to polymerize at room temperature inapproximately 40 minutes, with ratios of epoxide to NH as high as 1 to 7or more. These gels were comparatively brittle and stiff, showed anormal range of % hydration at approximately 400% consistent with ourstandard gel formulation

Initial actuation testing of new composite actuator structures comprisedof a hydrophilic actuator polymer and a hydrophobic polymer depictedgraphically in FIG. 1B successfully showed 100% swelling at eachactuator portion under positive electric current of 1 mA. Accordingly,an addressable location peristaltic type of pump mechanism, or an arrayof actuators as shown in FIG. 1C may effectively be constructed of theexamined composite polymers. Similarly, the examined polymers were shownto be smart and chemical responsive hydrogels, capable of being used ina variety of applications. Materials comprising these polymers may becast in many layers and shapes that would be advantageous to aparticular use and application.

In another embodiment of the invention, two or more of the di-epoxidesare combined into one singular polymer actuator composition and theperformance of the actuator material is adjusted according to the ratioof the dominant functional di-epoxide to the lesser functionaldi-epoxide. The ratio of the dominant functional di-epoxide to thelesser functional di-epoxide may be varied to advantageously varyactuation speed or flexibility of the material. In a particularembodiment, 1% neopentyl glycol diglycidyl ether is added to the JEFFAMINE® T403 and PEGDE formulation mentioned in previousPCT/US2007/073188, resulting in a much faster actuator. This is notintended to limit the use or the materials used in a composite assemblymade by cross-linking the functional layers.

A composite hydrogel material may be used as a sensor materialstructure, gel electrolyte material, selective ion permeable membrane,liquid filtration and treatment, wound care membrane, actuator or evenacid scavenging material. This process also may be used to seal theexternal layer or layers of a composite structure such as an actuatorthereby effectively sealing in the electrolyte held within or around thepolymer to protect from evaporation. Additionally, internal materialsmay be protected from the external environment by UV exposure protectionusing the described composite hydrogels. The embodiments described aboveare just a few examples for which the composite hydrogel of theinvention may be used for and are not meant to limit the scope of theinvention.

In one application, the present invention concerns improvements made toa polymeric actuator including an increase in effective surface area toincrease magnitude and repeatability of an expansion rate of a polymericactuator. This has been accomplished by increasing the actual surfacearea of the polymer and by increasing the effective surface area,electrode improvements, and by gas mitigation methods. The improvementsof this invention have been demonstrated to achieve a 400% increase in avolumetric expansion rate over prior art methods while reducingvariability.

An exemplary embodiment of an actuator assembly 100 according to thepresent invention is schematically depicted with respect to FIG. 2A.Actuator assembly 100 includes a polymeric actuator material 113 and anassociated electrode set including top electrode 106 and bottomelectrode 108. Bottom electrode is in contact with metal hydridematerial 110. The electrode set and the polymeric actuator 113 arecontained within housing 114. The housing 114 may be formed with folds,pleats or other excess material on the sides in order to allow for thelarge expansion rates of the actuator material as well as providingstorage pockets or areas for any excess gas generated to collect withoutimpacting the expansion rate of the actuator assembly. An electrolyte112 is also contained within housing 114 in contact with the electrodeset (106, 108) and actuator 113. Actuator 113 is a polymerized polymeractuator particulate made by grinding hydrated epoxy gel, and placingthe gel into a flexible porous bag 116. The actuator 113 may also becomprised of two or more of the di-epoxides described above to vary theperformance of the actuator material. Bag 116 is made of wovenpolypropylene mesh 116, 0.006″ thick with 150 micron hole sizes and heatsealed. One or more bags can be used in the configuration to takeadvantage of volume and stroke aspects. A porous separator membrane 115separates the pH gradient between electrode 108 and opposing electrode106 while still allowing contiguous electrolyte 112.

Polymeric actuator 113 will expand or contract in response to a changein the electrolyte 112. There are several types of polymeric actuators113 that may be used, including an “acid-responsive” polymeric actuatorand a “base-responsive” polymeric actuator. An “acid-responsive”polymeric actuator expands in response to a decreased pH in electrolyte112 surrounding polymeric actuator 113. This can be accomplished byproviding a positive bias of electrode 106 relative to electrode 108.Applying the positive bias causes current to flow from electrode 106 toelectrode 108 and causes a positive ion (H+) concentration in theelectrolyte 112 surrounding actuator 113 to increase. The voltageapplied between electrodes arranged in the aqueous solution consumeshydrogen ion and/or hydroxide ion as a result of electrode reaction oryields a concentration gradient due to electric double layer occurringon the surfaces of the electrodes, thereby changing the pH in thevicinity of the electrodes. Thus the electrolyte surrounding actuator113 becomes more acidic (lower pH) and causes actuator 113 to expand.

Since the expansion speed of a solid polymer gel block is limited by theability of the electrolyte or solvent to diffuse through the polymeractuator the speed of actuation may be increased by increasing thesurface area of the polymer actuator material with access to theelectrolyte. If the electrical bias is reversed, the positive ion flowreverses and electrolyte 112 surrounding actuator 113 becomes more basic(or less acidic) which causes an opposite or reverse effect on actuator113.

A “base-responsive” polymeric actuator 113 also may be used. In thatcase, applying a negative bias to electrode 106 relative to electrode108 will cause the pH in the electrolyte 112 surrounding polymericactuator to increase which will in turn cause the base-responsivepolymeric actuator 113 to expand. In this case the metal hydride 110would be in contact with the electrode 106 in an aqueous electrolytesolution depending on the electrolyte, electrochemical reaction and typeof gas produced during operation. When the polymeric actuator 113expands, it causes the entire actuator assembly 100 to expand.

An alternative design of an actuator assembly 120 utilizing both acidresponsive and base responsive actuators is depicted in FIG. 2B inschematic form. Actuator assembly 120 includes an acid responsivepolymeric actuator cast gel 123A, a base responsive polymeric actuatorcast gel 123B, a top electrode 128, and a bottom electrode 126 incontact with metal hydride 121 and then exiting the housing, all withinhousing 124. An electrolyte 122A surrounds top electrode 128 and acidresponsive actuator 123A; a bottom electrolyte 122B surrounds bottomelectrode 126 and base responsive actuator 123B. A porous separatormembrane 125 separates the top electrolyte 122 A from the bottomelectrolyte 122B while allowing ions to flow between electrolytes.

When a positive bias current is applied between top electrode 128 andbottom electrode 126 the pH of the top electrolyte 122A decreases whilethe pH of the bottom electrolyte 122B increases. The decreased pH(acidity increase) of top electrolyte 122A causes acid responsivepolymer material 123A to expand while the increased pH (more basic) ofbottom electrolyte 122B causes base responsive polymer material 123B toexpand. Having two layers of actuators may double the total displacementobtainable for the entire actuator assembly 120. It is anticipated thatadditional layers of polymeric actuators with alternating layers of acidresponsive and base responsive polymeric actuators can be used tofurther increase the maximum aggregate expansion of actuator assembly120.

An alternative embodiment of an actuator assembly 130 is depicted withrespect to FIG. 2C and includes the same embodiment of actuator assemblyshown in FIG. 2A with the addition of a top electrode 136 with metalhydride material 131A in contact with top electrode 136, as well as thebottom electrode 138.

An alternative embodiment of an actuator assembly 130 is depicted withrespect to FIG. 2C and includes the same embodiment of actuator assemblyshown in FIG. 2A with the polymer actuator material as a cast gel, it isalso possible to use multiple actuator material castings or bags in thesame configuration, the same would be true for all of the configurationsdepicted, also shown is a top electrode 136 with metal hydride material131A in contact with top electrode 136, as well as the bottom electrode138.

Another polymer actuator assembly embodiment is shown in FIG. 3A whereinthe top electrode 206 is in close proximity to gas adsorbing material215 such as an activated carbon which can adsorb, for example, oxygenwhen wet. The gas adsorbing material is in contact with electrolyte 212and adsorbs gas produced at electrode 206 as the gas migrates throughelectrolyte 212. Bottom electrode 208 is in contact with metal hydridematerial 210. The electrode set and the polymeric actuator material as acast gel 213 are contained within housing 214. Contained within housing214 is an electrolyte 212 in contact with the electrode set and actuatormaterial 213. Separating electrode 208 from surrounding electrolyte 212is a porous separator membrane 215. Polymeric actuator 213 will expandor contract in response to a change in the electrolyte 212, utilizingthe same type of actuation mechanism and response described for FIG. 2A.

Yet another preferred polymer actuator assembly embodiment is shown inFIG. 3B wherein the actuator material 230 is a polymer particulate heldin a porous flexible bag 223 and then the polymer particulate containingbag 223 is held in a firm porous structure 229 helping to contain anddirect the swelling flexible bag 223 in one direction during the polymermaterial's 230 actuation response for efficiency of stroke or improveddistance that the plate 228 can be pushed by flexible bag 223 expandingdue to the swelling of the polymer material 230. The Top electrode 206is inserted into the particulate bag 223 between the polymer particles230 to maximize contact.

The assembly 224 is vented into another gas absorbing material 227 suchas “Oxisorb” liquid form oxygen absorbent. The gas absorbent 227 isseparated from the electrolyte by hydrophobic separator materials 226that allow gas to penetrate while constraining electrolyte fluid. It ispossible also to have no absorbent 227 in the vent in order to merelycontain the gas in a separated compartment so the gas does not impactthe actuation of the polymer materials. The separator material 226 is incontact with electrolyte 222 and allows gas produced at electrode 206 tocollect as the gas migrates through electrolyte 222. Bottom electrode208 is in contact with metal hydride material 221 which allows gas toadsorb to the metal hydride material 221. The electrode set (206, 208)and the polymeric actuator 223 are contained within housing 224 incontact with an electrolyte 222. A porous membrane 225 may separateelectrode 208 from surrounding electrolyte 222.

Shown in all figures is the electrical power supply 101 and controller103 for control of the actuator assembly's motion, speed and force. Theembodiment in FIG. 3B also shows interaction with a sensor 105 forfeedback and automated control of the actuator assembly.

There are many gas mitigation materials and techniques that are wellknown in the art of various analytical sciences and methods such as HPLCor other methods of chromatography, all of the embodiments described aremeant to show possible actuator assembly configurations utilizing gasmitigation materials, components and techniques as part of the assemblyand are not meant to limit the scope of the invention in any way.

In another aspect of the present invention, an electrode capable ofdouble layer capacitance or charge storage is used to control gasgeneration within the actuator. For example, psuedocapacitor typeelectrodes may be used to control gas generation.

According to the present invention the electrical current builds acharge layer instead of generating gas at the electrolyte and electrodesurface interface. This process continues until the electrode is fullycharged, at which point, the charge is disbursed and the gas isproduced.

As seen in the example shown in FIG. 4, the actuator assembly iscontained in a flexible non permeable housing material 302 such as (butnot limited to) a metalized polyethylene film. The housing contains theelectrolyte 308, polymer actuator material 301, semi porous containerfor the polymer 303, the electrode in contact with or in the vicinity ofthe polymer 304, a semi porous separator membrane or sheet 305 locatedbetween the electrodes, a carbon PTFE capacitive layer coating 306 andthe opposing electrode 307 in electrical connection with dischargecircuit 309, controller and power source.

In one example of the present aspect of the invention, the electrode isdischarged at a predetermined time in the charge cycle. In this example,the point at which the gas is generated is a function of thepredetermined time, rather than the rate at which the energy accumulateswithin the capacitor. Once the discharge occurs, the charging processstarts again, thereby eliminating gas generation at the electrode byusing charge and discharge cycles.

To manufacture this type of electrode, a Teflon (PTFE) aqueous emulsion,such as those made by DuPont, is mixed with a high surface area carbonor other high surface area material, such as, for example, activatedcarbon; oxides such as, for example, metal oxides; as well as othermaterials such as metal hydrides. These materials can be used either ontheir own or mixed together to produce a desired performance curve ofgas mitigation at the electrode. The high surface area material is mixedwith the emulsion and pressed or coated onto the electrode and baked tothe correct processing temperature to bind the mixture together and tothe electrode, this process is well known in the art of battery andcapacitor manufacturing. The electrode substrate can be perforated,expanded or plated with solid metals (such as but not limited a low costaluminum or stainless steel foil), such as is well known in the art.

It should be emphasized that the above-described embodiments of thepresent invention, particularly, any “preferred” embodiments, are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the present invention. Manyvariations and modifications may be made to the above-describedembodiments without departing substantially from the spirit andprinciples of the invention. All such modifications and variations areintended to be included herein within the scope of this invention andprotected by the following claims.

What is claimed is:
 1. An actuator assembly comprising, an anodeelectrode and a cathode electrode, an electrolyte and a volume changingpolymeric actuator in contact with the anode electrode or the cathodeelectrode, wherein the electrodes are separated from each other by aporous membrane that facilitates modulation of the pH via charges orionic separation.
 2. An actuator assembly of claim 1 further comprisinga metal hydride material in contact with and covering a surface of oneor more of the electrodes.
 3. The actuator assembly of claim 2, furthercomprising a sealed flexible outer housing enclosing the electrolyte,the anode electrode, the cathode electrode, and the volume changingpolymeric actuator, allowing sealed entrance or exit points for theelectrodes, wherein the volume changing polymeric actuator is configuredto expand or contract in response to pH or chemical changes in theelectrolyte induced by an electrical potential differential.
 4. Theactuator assembly of claim 3, characterized by one or more of thefollowing features: (a) further comprising a second volume changingpolymeric actuator, wherein the volume changing polymeric actuators areeach adjacent to one of the electrodes and are separated from each otherby the porous membrane; and wherein the volume changing polymericactuators are configured to expand or contract simultaneously when theelectric potential differential is applied; (b) wherein the volumechanging polymeric actuator and the electrode in contact with thepolymeric actuator are sealed inside a flexible container or bag made ofthe same material as the porous membrane; and wherein a portion of theelectrode exiting the flexible container is continuously insulated fromthe electrolyte; wherein the flexible container or bag, or a portion ofthe flexible container or bag, preferably is comprised of an elastomericmaterial; (c) further comprising a rigid structure at least partiallysurrounding the volume changing polymer actuator material to facilitatea direction of actuation; wherein the rigid structure is pervious to theelectrolyte, wherein at least a portion of the rigid structurepreferably is porous; (d) wherein the volume changing polymeric actuatoris comprised of particulates of an actuating material, the particulatesof the actuating material and the electrolyte form a slurry, and whereinthe actuator assembly further comprises a flexible and porous enclosurehaving an interior and an exterior, wherein the particulates ofactuating material are contained in the enclosure interior, wherein oneof the electrodes preferably is in contact with a surface of theenclosure exterior or in contact with the polymer actuator particulatewithin the enclosure interior, and/or wherein the enclosure is containedwithin a rigid porous container that allows fluidic access of theelectrolyte to the actuating material within the enclosure.
 5. Theactuator assembly of claim 3, further comprising a gas adsorbant, and/orfurther comprising a storage area outside of the sealed flexible outerhousing in fluid connection with the electrolyte inside the sealedflexible outer housing.
 6. The actuator assembly of claim 1,characterized by one or more of the following features: (a) wherein theelectrodes of the actuator assembly are configured to allow in-lineelectrical connectivity of the actuator assembly with at least one otheractuator assembly; (b) wherein the electrolyte comprises an aqueoussolution; (c) wherein the electrolyte comprises a non-aqueous solution;(d) wherein the polymeric actuator drives a platen or piston, whereinthe platen or piston preferably pumps a fluid; and (e) furthercomprising a power source and a programmable controller, and optionallyfurther comprising one or more sensors communicating feedback to thecontroller.
 7. A polymeric actuator assembly comprising: a housing; afirst electrode in contact with a first portion of an electrolyte; asecond electrode in contact with a second portion of the electrolyte; amembrane separating the first portion of the electrolyte from the secondportion of the electrolyte to support a pH difference between the firstand second portions of the electrolyte when a voltage is applied betweenthe first and second electrodes; a plurality of polymeric actuatorsdisposed in the first portion of the electrolyte and configured tochange volume in response to a pH change within the first portion of theelectrolyte.
 8. The polymeric actuator of claim 7, wherein at least oneof the polymeric actuators comprises granules of a polymeric actuatingmaterial contained within a porous container, wherein the porouscontainer preferably is a polymeric bag, and wherein the granules ofpolymeric actuating materials preferably comprise a slurry with theelectrolyte.
 9. A polymeric actuator component comprising (a) anactuating polymer that increases volume in response to a stimulus, crosslinked to a hydrophobic polymer, or (b) a NH reactant and an epoxide,wherein the epoxide comprises a hydrophilic ether and a hydrophobicether.
 10. The polymeric actuator component of claim 9 (a), wherein theactuating polymer and the hydrophobic polymer comprise an NH reactantand an epoxide.
 11. The polymeric actuator component of claim 10,characterized by one or more of the following features: (a) wherein theNH reactant in the actuating polymer and the NH reactant in thehydrophobic polymer comprise the same NH reactant; (b) wherein theepoxide in the actuating polymer comprises polyethylene diglycidylglycol ether; (c) wherein the epoxide in the hydrophobic polymercomprises either neopentyl diglycidyl ether or polypropylene diglycidylglycol ether; (d) wherein the NH reactant in the hydrophobic polymercomprises a polyether amine, (e) wherein the NH reactant in the actuatorpolymer comprises a polyether amine, wherein the NH reactant preferablycomprises a polyether amine, more preferably a polyoxyalkyleneamine; (f)wherein the ratio of epoxide to NH reactant in the hydrophobic polymeris between about 1 to 1.5 and about 1 to 4, wherein the hydrophobicpolymer preferably is oriented to protect the hydrophilic polymer fromthe external environment, and/or wherein the hydrophobic polymer sealsthe actuator polymer in a defined volume, and (g) wherein the ratio ofepoxide to NH reactant in the hydrophobic polymer is about 1 to 2.0,wherein the hydrophobic polymer preferably comprises polyethyleneamineand water.
 12. The polymeric actuator material of claim 9(b),characterized by one or both of the following features: (a) wherein theratio of epoxide to NH reactant is about 1 to 2.85; (b) wherein theratio of hydrophilic ether to hydrophobic ether is about 99 to
 1. 13. Apolymer actuator assembly of claim 7, comprising one or more polymeractuators, each actuator having one or more double layer capacitorelectrodes.
 14. The polymer actuator assembly of claim 13, wherein thepolymer actuators are connected in series, forming a pump.